Input from the charm threshold for the measurement of $\gamma$

A brief overview of the inputs from charm threshold that are essential to the determination of the Unitarity Triangle angle $\gamma$ is presented. The focus is on the measurements of four-body final states that have not previously been considered: $D^0\to K_{\rm S}^0 \pi^+ \pi^- \pi^0$ and $D^0 \to \pi^+ \pi^- \pi^+ \pi^-$.